Magnetic and dielectric properties of Mn0.2Ni0.8Fe2O4 nanoparticles synthesized by PEG-assisted hydrothermal method

We present a systematic investigation on the structural and magnetic properties of Mn0.2Ni0.8Fe2O4 nanoparticles synthesized by a polyethylene glycol (PEG)-assisted hydrothermal route. XRD, FT-IR, TEM and VSM were used for the structural, morphological, dielectric properties and magnetic investigation of the products, respectively. Average crystallite size of product was estimated using Line profile fitting as 6 +/- A 1 nm and particle size as 6.5 +/- A 1.0 nm from TEM micrographs. Magnetization measurements have shown that the particles have a blocking temperature of 134 K. Magnetization and the coercive field of the sample increase by decreasing the temperature. The conductivity measurements reveal the semiconducting behaviour for the sample. Temperature-dependent dielectric properties: dielectric permittivity (epsilon) and ac conductivity (sigma(ac)) for the sample were studied as a function of applied frequency in the range from 1 Hz to 3 MHz. These studies indicated that the dielectric dispersion curve for the sample showed usual dielectric dispersion which can be explained on the basis of Koop's theory, which is based on the Maxwell-Wagner model for the interfacial polarization of homogeneous double structure.